# STDEVSAMPIF Function

Generates the standard deviation of values by group in a column that meet a specific condition using the sample statistical method.

**Nota**

When added to a transform, this function is applied to the sample in the data grid. If you change your sample or run the job, the computed values for this function are updated. Transforms that change the number of rows in subsequent recipe steps do not affect the values computed for this step.

**Nota**

This function applies to a sample of the entire population. More information is below.

Terms...

**Relevant terms:**

Term | Description |
---|---|

Population | Population statistical functions are computed from all possible values. See https://en.wikipedia.org/wiki/Statistical_population. |

Sample | Sample-based statistical functions are computed from a subset or sample of all values. See https://en.wikipedia.org/wiki/Sampling_(statistics). These function names include
Statistical sampling has no relationship to the samples taken within the product. When statistical functions are computed during job execution, they are applied across the entire dataset. Sample method calculations are computed at that time. |

This function is calculated across a sample of all values.

For more information on a population version of this function, see STDEVIF Function.

**Wrangle vs. SQL:** This function is part of Wrangle, a proprietary data transformation language. Wrangle is not SQL. For more information, see Wrangle Language.

## Basic Usage

<span>stdevsampif</span>(testScores, testScores > 0)

**Output:** Returns the standard deviation of the`testScores`

column when the`testScores`

value is greater than 0.

## Syntax and Arguments

stdevsampif(col_ref, test_expression) [group:group_col_ref] [limit:limit_count]

Argument | Required? | Data Type | Description |
---|---|---|---|

col_ref | Y | string | Reference to the column you wish to evaluate. |

test_expression | Y | string | Expression that is evaluated. Must resolve to |

For more information on syntax standards, see Language Documentation Syntax Notes.

For more information on the `group`

and `limit`

parameters, see Pivot Transform.

### col_ref

Name of the column whose values you wish to use in the calculation. Column must be a numeric (Integer or Decimal) type.

** Usage Notes:**

Required? | Data Type | Example Value |
---|---|---|

Yes | String that corresponds to the name of the column | myValues |

### test_expression

This parameter contains the expression to evaluate. This expression must resolve to a Boolean (`true`

or `false`

) value.

** Usage Notes:**

Required? | Data Type | Example Value |
---|---|---|

Yes | String expression that evaluates to | (LastName == 'Mouse' && FirstName == 'Mickey') |

## Examples

**Suggerimento**

For additional examples, see Common Tasks.

### Example - Conditional Calculation Functions

This example shows some of the statistical functions that use the sample method of computation.

**Functions**:

Item | Description |
---|---|

STDEVSAMP Function | Computes the standard deviation across column values of Integer or Decimal type using the sample statistical method. |

VARSAMP Function | Computes the variance among all values in a column using the sample statistical method. Input column can be of Integer or Decimal. If no numeric values are detected in the input column, the function returns |

STDEVSAMPIF Function | Generates the standard deviation of values by group in a column that meet a specific condition using the sample statistical method. |

VARSAMPIF Function | Generates the variance of values by group in a column that meet a specific condition using the sample statistical method. |

ROUND Function | Rounds input value to the nearest integer. Input can be an Integer, a Decimal, a column reference, or an expression. Optional second argument can be used to specify the number of digits to which to round. |

**Source:**

Students took tests on three consecutive Saturdays:

Student | Date | Score |
---|---|---|

Andrew | 11/9/19 | 81 |

Bella | 11/9/19 | 84 |

Christina | 11/9/19 | 79 |

David | 11/9/19 | 64 |

Ellen | 11/9/19 | 61 |

Fred | 11/9/19 | 63 |

Andrew | 11/16/19 | 73 |

Bella | 11/16/19 | 88 |

Christina | 11/16/19 | 78 |

David | 11/16/19 | 67 |

Ellen | 11/16/19 | 87 |

Fred | 11/16/19 | 90 |

Andrew | 11/23/19 | 76 |

Bella | 11/23/19 | 93 |

Christina | 11/23/19 | 81 |

David | 11/23/19 | 97 |

Ellen | 11/23/19 | 97 |

Fred | 11/23/19 | 91 |

**Transformation:**

You can use the following transformations to calculate standard deviation and variance across all dates using the sample method. Each computation has been rounded to three digits.

Transformation Name | |
---|---|

Parameter: Formula type | Single row formula |

Parameter: Formula | round(stdevsamp(Score), 3) |

Parameter: New column name | 'stdevSamp' |

Transformation Name | |
---|---|

Parameter: Formula type | Single row formula |

Parameter: Formula | round(varsamp(Score), 3) |

Parameter: New column name | 'varSamp' |

You can use the following to limit the previous statistical computations to the last two Saturdays of testing:

Transformation Name | |
---|---|

Parameter: Formula type | Single row formula |

Parameter: Formula | round(stdevsampif(Score, Date != '11\/9\/2019'), 3) |

Parameter: New column name | 'stdevSampIf' |

Transformation Name | |
---|---|

Parameter: Formula type | Single row formula |

Parameter: Formula | round(varsampif(Score, Date != '11\/9\/2019'), 3) |

Parameter: New column name | 'varSampIf' |

**Results:**

Student | Date | Score | varSampIf | stdevSampIf | varSamp | stdevSamp |
---|---|---|---|---|---|---|

Andrew | 11/9/19 | 81 | 94.515 | 9.722 | 131.673 | 11.475 |

Bella | 11/9/19 | 84 | 94.515 | 9.722 | 131.673 | 11.475 |

Christina | 11/9/19 | 79 | 94.515 | 9.722 | 131.673 | 11.475 |

David | 11/9/19 | 64 | 94.515 | 9.722 | 131.673 | 11.475 |

Ellen | 11/9/19 | 61 | 94.515 | 9.722 | 131.673 | 11.475 |

Fred | 11/9/19 | 63 | 94.515 | 9.722 | 131.673 | 11.475 |

Andrew | 11/16/19 | 73 | 94.515 | 9.722 | 131.673 | 11.475 |

Bella | 11/16/19 | 88 | 94.515 | 9.722 | 131.673 | 11.475 |

Christina | 11/16/19 | 78 | 94.515 | 9.722 | 131.673 | 11.475 |

David | 11/16/19 | 67 | 94.515 | 9.722 | 131.673 | 11.475 |

Ellen | 11/16/19 | 87 | 94.515 | 9.722 | 131.673 | 11.475 |

Fred | 11/16/19 | 90 | 94.515 | 9.722 | 131.673 | 11.475 |

Andrew | 11/23/19 | 76 | 94.515 | 9.722 | 131.673 | 11.475 |

Bella | 11/23/19 | 93 | 94.515 | 9.722 | 131.673 | 11.475 |

Christina | 11/23/19 | 81 | 94.515 | 9.722 | 131.673 | 11.475 |

David | 11/23/19 | 97 | 94.515 | 9.722 | 131.673 | 11.475 |

Ellen | 11/23/19 | 97 | 94.515 | 9.722 | 131.673 | 11.475 |

Fred | 11/23/19 | 91 | 94.515 | 9.722 | 131.673 | 11.475 |